The Cretaceous Period

The Cretaceous Period is part of the Phanerozoic Eon and is the final period of the Mesozoic Era. It covered the time span of 145 million years ago to 65 million years ago. At the end of the Jurassic Period, there was a minor mass extinction of bivalved mollusks which marked the beginning of the Cretaceous Period. At the end of the Cretaceous Period, there was the mass extinction of dinosaurs, ammonoids, and many land plants.